How to map the result of jooq multiset into Hashmap(Java Map)?-CodePudding

I have the following class and query. I want to use multiset to map the result of the images into Map<String, String>(Key: OrderNumber / Value: FileKey), but I don't know how to do it. Could you help me how to map the multiset result into hashmap?

data class User(
  val id: UUID,
  val name: String,
  val images: Map<String, String>?
)

@Repository
@Transactional(readOnly = true)
class FetchUserRepository(private val ctx: DSLContext) {
  private val user = JUser.USER
  private val userImage = JUserImage.USER_IMAGE 

  override fun fetch(): List<User> {
    return ctx.select(
      user.ID,
      user.NAME,
      multiset(
        select(userImage.ORDER_NUMBER.cast(String::class.java), userImage.FILE_KEY)
          .from(userImage)
          .where(userImage.USER_ID.eq(user.ID))
      ).convertFrom { r -> r.map(mapping(???)) } // I'm not sure how to map the result to hashmap
    )
      .from(user)
      .fetchInto(User::class.java)
  }

CodePudding user response：

The type of your multiset() expression is Result<Record2<String, String>>, so you can use the Result.intoMap(Field, Field) method, or even Result.collect(Collector) using the Records.intoMap() collector, which allows for avoiding the repetition of field names:

{ r -> r.collect(Records.intoMap()) }

I've explained this more in detail in a blog post, here. In fact, this seems so useful and powerful, let's add some convenience on top of the existing API using some extensions (located in the jOOQ-kotlin extensions module):

// New extension functions, e.g.
fun <R : Record, E> Field<Result<R>>.collecting(collector: Collector<R, *, E>)
  = convertFrom { it.collect(collector) }

fun <K, V> Field<Result<Record2<K, V>>>.intoMap(): Field<Map<K, V>> 
  = collecting(Records.intoMap())

// And then, you can write:
multiset(...).intoMap()

The feature request is here: https://github.com/jOOQ/jOOQ/issues/13538